Salt in Fresh Water Pool

[hamop78]

See my signature for pool specs.

Location Central PA
BBB since 2004 And Ben
I add 8.25% bleach (Clorox) and Muriatic acid automatically with CAT based on ORP and pH.

Now the issue.
I started getting corrosion on the aluminum coping which appeared to be coming from the inside out (Concrete around pool).
I hired the original pool installer to make repairs. When he arrived he told me my water was messed up (his language was a bit more harsh). They took a water sample and went about filling the holes with body putty and then spot painted.
I sampled also and got FC=3.6, CC=0 pH=7.5 Alk=90 CYA=20 (all by Taylor Titration) TDS=175 (Electronic). I do not bother with calcium hardness since it's a vinyl liner pool.
The Pool company secretary called me later and told me to dump 7 bags of salt in the pool (They obviously messed that up since it's a fresh water pool) and said my Salt was 1400 PPM.
I took a sample to a different company and they also got 1400 PPM salt??? They also showed TDS was 1850??

My question is -- Where did the salt come from?? I have never changed out the water since installation in 2002-- Just rain and well water from a hose to compensate for evaporation.
Would this be a result of the Sodium component of the bleach?? And what can I do to lower the salt level if that's the issue.

I'd appreciate any expert advice.

 

[woodyp]

How are you chlorinating your pool?

 

[hamop78]

Yep -- see original post
BBB --- 8.25% bleach from automatic controller based on ORP

 

[pooldv]

Chlorine and muriatic acid slowly add salt over time. There could be some in your well water too. To lower salt level you have to drain water and replace. No reason to though, 1400 ppm of salt isn't hurting anything and it makes your water a little easier on your skin and eyes. I would raise CYA to 30 or 40. The most important thing to avoid corrosion is to maintain PH between 7.2 and 7.8 with 7.6 to 7.8 being ideal. PH below 7.0 is corrosive to pool equipment.

 

[hamop78]

Thanks --- I doubt if my pH has ever been "out of spec" except when doing stain removal at the end of the season every 3 or 4 years and their are no swimmers when I do that.
If anything it'll go high (pH) if I'm not paying attention to the acid supply tank and it runs out.
I think the Pool company instant analysis is unfounded ---- but since they are the "Professionals" and know all (especially selling their Pool Junk)..............
Again Thanks for your weigh-in --- Maybe Chem Geek will chime in with a chemistry lesson. I envy his pool wisdom

 

[basod]

Bleach starts its life as salt and breaks back down into salt as its disenfecting capacity is used up.
ETA. Every gallon of 8.25 bleach you add based on your pool volume increases salt by 5.2

 

[hamop78]

Thanks --- I doubt if my pH has ever been "out of spec" except when doing stain removal at the end of the season every 3 or 4 years and their are no swimmers when I do that.
If anything it'll go high (pH) if I'm not paying attention to the acid supply tank and it runs out.
I think the Pool company instant analysis is unfounded ---- but since they are the "Professionals" and know all (especially selling their Pool Junk)..............
Again Thanks for your weigh-in --- Maybe Chem Geek will chime in with a chemistry lesson. I envy his pool wisdom

Chlorine and muriatic acid slowly add salt over time. There could be some in your well water too. To lower salt level you have to drain water and replace. No reason to though, 1400 ppm of salt isn't hurting anything and it makes your water a little easier on your skin and eyes. I would raise CYA to 30 or 40. The most important thing to avoid corrosion is to maintain PH between 7.2 and 7.8 with 7.6 to 7.8 being ideal. PH below 7.0 is corrosive to pool equipment.

Bleach starts its life as salt and breaks back down into salt as its disenfecting capacity is used up.
ETA. Every gallon of 8.25 bleach you add based on pool your pool volume increasing salt by 5.2

In my previous lifetime about (50 years ago) I worked at a chemical company in Houston TX and we made commercial bleach ---- If I remember (and I might not--- senior moments) we used Sodium Hydroxide (caustic soda) (NAOH) and injected liquid chlorine (CL2) into it --- this created an exothermic reaction producing heat and about 15% bleach. I remember we would try for a higher percentage but it would break done quickly and the bosses would raise -----
Anyway -- I have no recollection of using salt but maybe that was how the caustic soda started.

Either way I thank you for the calculation. Interpolating from your calculation I should have used 269.2 Gallons of 8.25% Bleach. I'm not sure I want to try to validate my purchases since 2004 since it started at 5% then 6.25 and now 8.25%.....I do know I go through about 30+ cases (3 * 121 oz) per summer.

WOW this makes my head hurt

Thanks again for your help.

 

[Divin Dave]

And of course through the process of dilution due to rain etc, the salt is also diluted. Then added back in after the rain/ overflow is over.... LOL. Which is why usually the salt level never gets overly high in a non-swg pool.

 

[basod]

In my previous lifetime about (50 years ago) I worked at a chemical company in Houston TX and we made commercial bleach ---- If I remember (and I might not--- senior moments) we used Sodium Hydroxide (caustic soda) (NAOH) and injected liquid chlorine (CL2) into it --- this created an exothermic reaction producing heat and about 15% bleach. I remember we would try for a higher percentage but it would break done quickly and the bosses would raise -----
Anyway -- I have no recollection of using salt but maybe that was how the caustic soda started.

Either way I thank you for the calculation. Interpolating from your calculation I should have used 269.2 Gallons of 8.25% Bleach. I'm not sure I want to try to validate my purchases since 2004 since it started at 5% then 6.25 and now 8.25%.....I do know I go through about 30+ cases (3 * 121 oz) per summer.

WOW this makes my head hurt

Thanks again for your help.

You are correct in the industrial process of making bleach. The inputs to the process NaOH and Cl2 are created by electrolysis using salt water. Salt to salt dust to dust enjoy your pool while on earth

 

[hamop78]

Thanks to all who responded to my issue. Lots of good info